Genetical studies on the skeleton of the mouse

Summary

• 1. Tie effects of changes in parental diet on skeletal variation in the offspring has been studied in mice of the inbred strains A and C 57 BL.

• 2. All three changes (to thiouracil in the drinking water of C57 BL mice, from a good cube diet to oats in C57 BL mice, from a good to a poorer cube diet in A strain mice) reduced the mean size of lower third molars. Results of fostering experiments and other data suggest that this is partly due to post-natal factors connected with the mother’s milk, which may even influence the size of first molars.

• 3. Bight out of eleven C57 BL skeletal anomalies were significantly affected by the clange to an oats diet, three becoming rarer and five more common, as shown in Table 6.

• 4. The frequency of dyssymphysis of the second thoracic vertebra increased from nil to 16% on the oats diet. In quite a different 057 BL substrain this anomaly is common on a normal diet; the oats diet thus produces a type of phenocopy.

• 5. 057 BL mice on thiouracil were somewhat retarded, but the only clear-cut effect of this substance on skeletal variation was an increase in the proportion of well-developed spinous processes on the second thoracic vertebra.

• 6. The relation of these results to previous work on maternal influences in pure lines and nutritional deficiency effects is discussed, also their bearing on taxonomic studies. I am glad of this opportunity to thank Dr H. Grüneberg for his continued interest in this work and for many helpful suggestions. This investigation was carried out during the tenure of an Agricultural Research Council grant, which is gratefully acknowledged.